Study On Influence Mechanism And Early-warning Model Of Low Temperature And Poor Light Stress On Leaves Of "Red Globe" Grape In Greenhouse

The greenhouse "Red Globe" grape was select as experimental material,the effects of stress and recovery under low temperature and poor light in physiological and biochemical parameters with grape leaves were studied from three aspects:photosynthesis characteristics,fluorescence characteristics and aging characteristics.The applicability of photosynthetic model and stomatal conductance model to grape leaves under stress environment was discussed,in order to reveale the response mechanism of grape leaves under low temperature and poor light stress.The indexes that reflect the degree of stress of grape leaves were selected,build greenhouse grape low temperature and poor light stress equation,and the stress level,then build the prediction model of the index(grade).The results can provide scientific basis for defense and fine services of low temperature and poor light meteorological disasters in Jiangsu facilities.The results are as follows:(1)Low temperature,poor light and low temperature and poor light stress all inhibited the net photosynthetic rate(Pn)of grape leaves.The decrease of Pn may be related to the limitation of stomata at the initial stage.The main influencing factor is the non-stomatal limitation when the stress level is deeper.Forcing the leaves of the grape to reduce the use of light intensity range,enhanced respiration,photosynthesis potential weakened,the light energy conversion efficiency under poor light.Poor light conditions increase the degree of weakening of photosynthetic ability of grapes under low temperature stress.The fitting effect of the light response curve is optimal with the right-angle hyperbolic correction model(R2?0.993),and the exponential model(R2?0.984)and non-right-angle hyperbolic model(R2?0.984)also have a good fitting effect,BB Both the model(R2?0.984)and the BBL(R?0.984)model can simulate the stomatal conductance.The latter model has a better simulation effect.The Jarvis model is superior to the BBLP coupled model in the simulation of stomatal conductance of grape leaves with photosynthetically active radiation changes.The model fitting effect worsens as the degree of stress increases.(2)The Fv/Fm and qP of PSll grapevine leaf PSll decreased with the increase of stress time and the decrease of temperature,but the trend of NPQ was opposite.Stress has less influence on Fv/Fm than qP and NPQ.Poor light can alleviate the effects of low temperature stress on the modulated fluorescence parameters of grape leaves.Under low temperature and poor light stress,the leaves mainly resisted the stress on the photosynthetic apparatus by increasing the heat dissipation of the antenna pigments.The force of the stress was used to reduce the energy of the PS? reaction center;the OJIP curve of the grape leaves was obviously deformed under low temperature and poor light stress.The relative variable fluorescence(AVt)curve showed that severe low-temperature and low-light stress reduced the ability of PS? to regulate heat dissipation;grape leaves oxygen-evolving complex(OEC)was damaged by low-temperature and low-temperature light stress,and poor light stress was not observed.Obvious efifect.PS? receptor side and donor side were less responsive to the stress than the reaction center.Grape leaf PSI has better stability in low temperature and poor light conditions.Both the relative activity of PSI and the efficiency of the PS? reaction center showed a decreasing trend.(3)POD and SOD responded quickly to stress,and the stress at 14/4? over 7d surpassed the SOD regulation range.With the increase of stress intensity,MDA increased and the chlorophyll content decreased.Stress has a greater effect on chlorophyll a than chlorophyll b.(4)The results of the principal component comprehensive scores of the 25 indicators in this study showed that CK>L>LT>T under the same stress time.Convenient for practical applications,the biological significance of the comprehensive indicators,the ease of measurement of the indicators,the correlation between the indicators,and their scores in the principal component analysis screened out as Pn5 Fv/Fm,Plabs,MDA,and Chl The indicators of the degree of stress on the grape leaves were obtained.The weight of each index was obtained through the second principal component analysis,and the stress index equation SI was constructed.The R2 of the total scores of the stress index and the principal component of each treatment is 0.97.According to the stress indexes of each treatment in the recovery period,the low-temperature and low-light disasters are divided into four levels:light,medium,heavy,and extremely heavy.(5)A low temperature and poor light stress degree index(grade)prediction model was constructed based on the physiological and biochemical response characteristics of grape leaves under low temperature and poor light stress.The model included low temperature,poor light stress,eold stress and stress resistance.The simulation of the SI during the treatment period(R2 = 0.086)was weaker than the recovery phase(R2 = 0.94).